There is a conventional air-conditioning apparatus that performs refrigeration cycle by using an “HFC refrigerant” such as nonflammable R410A. Unlike an “HCFC refrigerant” such as conventionally used R22, this R410A has zero ozone depletion potential (hereinafter referred to as an “ODP”), and thus, does not damage the ozone layer, but has a high global warming potential (hereinafter referred to as a “GWP”). Thus, as a part of prevention of global warming, it has been investigated to shift from an HFC refrigerant having a high GWP, such as R410A, to a refrigerant having a low GWP (hereinafter referred to as a low-GWP refrigerant).
Candidates for a low-GWP refrigerant include an HC refrigerant such as R290 (C3H8: propane) and R1270 (C3H6: propylene), which are natural refrigerants. Unlike nonflammable R410A, however, such HC refrigerants are extremely flammable, and thus, a caution and measures are needed against refrigerant leakage.
Candidates for a low-GWP refrigerant also include an HFC refrigerant having no double bonds of carbon in its composition, such as R32 (CH2F2: difluoromethane) having a GWP lower than that of R410A.
Candidates of similar refrigerants include halogenated hydrocarbon that is a type of an HFC refrigerant similar to R32 and has double bonds of carbon in its composition. Examples of such halogenated hydrocarbon include HFO-1234yf (CF3CF═CH2: tetrafluoropropene) and HFO-1234ze (CF3—CH═CHF). To distinguish from an HFC refrigerant such as R32 having no double bonds of carbon in its composition, an HFC refrigerant having double bonds of carbon is often referred to as an “HFO refrigerant” using “O” that stands for olefin (where unsaturated hydrocarbon having double bonds of carbon is called olefin).
Such a low-GWP refrigerant (such as an HFC refrigerant and an HFO refrigerant) is not as highly flammable as an HC refrigerant exemplified by R290 (C3H8: propane), which is a natural refrigerant, but unlike nonflammable R410A, has a flammability at a slightly flammable level. Thus, similarly to R290, a caution is also needed against refrigerant leakage. Refrigerant having flammability, including refrigerants at slightly flammable levels, will be hereinafter referred to as “flammable refrigerant.”
In the case of using these flammable refrigerants, required standards are different from those of conventional apparatuses, and thus, a caution is needed in application. In particular, it is not desirable in terms of safety to permit an air-conditioning apparatus of an air-conditioning apparatus with a flow of a flammable refrigerant in an outdoor unit or an indoor unit provided with no fire protection units.
Thus, an air-conditioning apparatus is proposed that can stop and issue a warning when an indoor unit provided with no fire protection units is connected to the air-conditioning apparatus by comparing information on flammability of a refrigerant usable in an outdoor unit and information on flammability of a refrigerant usable in an indoor unit (see, for example, Patent Literature 1). The air-conditioning apparatus disclosed in Patent Literature 1 compares flammabilities of refrigerants usable in the outdoor unit and the indoor unit, and permits connection only when safety is assured.